[Changes in the circadian rhythm of the hypothalamo-pituitary-adrenal system at lengthy intervals after irradiation].

The disturbance of circadian rhythm of the hypophysis-adrenal system (e. g. the absence of an evening fall in the corticosterone content of blood) was observed 3, 6 and 12 months after irradiation of rats (1186 X 10(-4) Ci/kg). Similar changes were noted in the control group of animals of the same age after 6 and 12 months. In the exposed animals, however, these changes were more frequent.